[jurban]

I'm designing the physical layout for running present and future circuits to assigned parking spots in a common garage for use with Electrical Vehicle (EV) charging stations. All will be 240 VAC. This is for a multi-unit dwelling in San Francisco, CA. with 25 parking spaces on two floors adjacent to the meters. Circuits and charging stations will be added incrementally as people purchase their EVs. The objective is to lower each unit's cost by establishing the common raceways to minimize the incremental labor and materials for each run. Additionally, the design should allow for each unit's owner to decide what service/product they would rather install instead of establishing a standard for the entire building. At the moment only one resident has the need for a charging station.

Option 1) One solution would be to run a single 4" conduit from the junction (near the bank of meters) so that each circuit could be pulled when required. One or more conduits would be run between the meter bank and the junction (about 5 ft). This is desirable because a concrete floor and wall lie between the meters and the parking garage. I suspect that combining separately-metered conductors into a single conduit violates code.

Option 2) Alternatively we install meters at each parking spot and extend the service drop/lateral into a junction in the middle of the garages' ceilings. Each parking spot would install a separate meter that taps into it. I suspect that arrangement exposes too much un-metered raceway to unauthorized taps. Inspectors would probably be uneasy with that arrangement.

Option 3) Finally, because the cost would be primarily in drilling through walls, a fire-rated pass-through could be installed and each conduit would be routed through it when required. This opens up a big hole into the floor and wall. Structurally it is undesirable and it would probably be expensive.

Option 4) The fall-back is to install each circuit incrementally and ultimately drill 50 (25 X 2) holes and run individual conduits to each parking spot.

Any guidance is appreciated.

 

[dronai]

The meters are mains only going to each unit load center correct ? How can you tap off of the mains before the load center ? You would need a 50A 240V tap per space ?

 

[emtnut]

I think you should hire a LEC, to let you know the pros and cons of a single conduit for all chargers, and the issue with a box with power in it but not going anywhere.

You'll be able to fully analyze the upfront, vs later charges, and proceed accordingly.

 

[jurban]

mains are only going to each unit load center

dronai,
The existing condition has all meters in one location on the bottom floor (7 fl bldg) and each connects to their respective units via separate conduit.
Option 2, in effect, is to establish a secondary set of meters.

emtnut,
That is the plan. I would rather get some perspective from a discussion board beforehand.

 

[splatz]

Interesting question. IMO, this is on the cusp of what you'd have an electrician expert in multi-family service design, and what you'd have an engineer design. I think I'd go with the engineer, have them work up a few options, and have the electrician that does the maintenance on the building price the options.

A few non technical points for consideration.

* Very hard to predict the future. Who knows what EV charging will look like if it ever reaches mass adoption?
* That said, oversize pipes are about as good futureproofing as there is.
* If you let each tenant's electrician do there own thing, it will be a succession of **** shows. If you pipe in everyone now, they'll most likely fall in line to some extent.
* Could the utility transformer handle a bunch of electric cars? That's the utility's headache to some extent but still.
* Are the tenant's services sized to accommodate the load? Should that be taken into consideration in your planning?
* Are there any subsidies available to capitalize on? If not maybe wait?

 

[jurban]

Pre-piping

Thanks Splatz!

Before I dig into the California electrical codes, do you (or anyone perusing this thread) have any insights into allowing circuits from different meters co-located in the same conduit? If that is OK (or maybe some alternative like armored cables instead of un-bundled wires) then that would be the solution.
Regardless of the future of EVs and charging, they will - by definition - require electricity. The only wrinkle (which is out of scope for the original post's questions) is if we intend to incorporate solar panels into the plan. IMHO that's too much to consider at the moment.